Vehicle fuel, such as diesel or petrol, is increasingly subject to theft due to increases in retail costs. Fuel theft is particularly problematic for the transport industry, due to costs of the fuel itself and due to loss of productivity.
Fuel theft can take a number of forms. Commonly, fuel theft is committed by siphoning fuel from a vehicle's tanks. This form of fuel theft may take place from either private vehicles or from commercial vehicles, but is most prevalent from commercial vehicles due to the comparably large capacity of their fuel tanks. In addition, small amounts of fuel siphoned from large capacity tanks may not have an obvious effect on the fuel level reading within the vehicle cockpit, and so fuel theft, or the location and time of fuel theft, may remain undetected.
In some cases, fuel theft is hidden by the addition of water to the fuel tank to replace stolen fuel. A vehicle fuel tank sensor reflects the total volume of liquid present in the tank and therefore does not immediately alert the driver or owner of the vehicle that a significant theft has occurred. In addition, water is immiscible with the fuel in the tank and therefore the vehicle continues to operate normally for a period of time, until sufficient water is delivered to the vehicle's engine to affect its operation, again making the time and location of the theft difficult to determine.
Alternatively, fuel may be introduced into portable tanks for later use or re-sale, during re-filling of a commercial or fleet vehicle and the cost fraudulently included in the much larger cost of refuelling the vehicle.
Various devices for the detection of fuel theft have been proposed. Anti-siphoning devices have been proposed for insertion into the necks of vehicle fuel tanks. Such devices cannot, however, prevent fuel from being intercepted at alternate points in the fuel system, for example by removal of a fuel tank drain plug, or temporary disconnection of a fuel line, or by methods resulting in permanent damage to the vehicle. Anti-siphon devices may therefore also encourage fuel theft by methods resulting in permanent damage to the vehicle, such that the costs incurred due to the permanent damage and down time of the vehicle exceed the cost of the fuel itself. Anti-siphon devices are also unable to prevent the other forms of fuel theft discussed above.
Devices have been proposed to directly monitor fuel tank levels over time and raise an alarm when an unexpected change of fuel has been recorded. Devices of this type require sensors to be installed within the fuel tank and wiring for the system to be installed throughout the vehicle. In addition to the cost and complexity of fitting systems of this type, it is difficult for them to remain undetected by a person familiar with the technology. Additionally, it is possible to avoid triggering such devices by removing fuel at one point in the system (for example from a fuel line) at a similar rate to which water is introduced elsewhere (for example through the neck of the fuel tank).
Fuel theft by fraudulently filling separate fuel cans, as described above, cannot be detected by any existing devices installed upon vehicles. Such behaviour may presently only be detected when it is so blatant as to become apparent from detailed comparison of miles travelled and volume of fuel purchased, or if an individual's fraudulent behaviour is directly observed. Since an individual may use, and may commit fuel theft from, a number of vehicles within a fleet, their behaviour may go unnoticed indefinitely.
Therefore, there remains a need for devices or systems for the detection of fuel theft capable of more effectively detecting fuel theft.